Recently, in the semiconductor device field based on semiconductors and liquid crystal devices, a tendency toward electronic devices having a high degree of integration, a high density, a high reliability, and a high speed is rapidly spreading and an active research is being done utilizing advantages of organic materials that allow for easy processability and higher purity.
A polyimide compound has excellent thermal stability, and excellent mechanical, electrical and chemical characteristics, and thus the use of a photosensitive insulating film as well as a photosensitive resin containing the polyimide compound has expanded not only to the field of semiconductors, but also to the field of displays.
A polyimide polymer is chiefly fabricated using a method comprising (1) obtaining a polyimide precursor solution by performing a 2-step condensation polymerization of a diamine component with a dianhydride component within a polar organic solvent, such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF), (2) coating the polyimide precursor solution on a silicon wafer or glass, and (3) curing the coating through thermal treatment. Polyimide products for commercialized electronic materials are supplied in the form of a polyimide precursor solution or a polyimide film. In the field of semiconductor devices, polyimide products are usually supplied in the form of a polyimide precursor solution.
A polyimide resin is applied to a buffer coating film of a semiconductor device.
A method of assigning photosensitivity to a polyimide resin that can be used in a photosensitive resin composition typically includes a method of chemically combining a crosslinkable function group with a polyimide precursor or a method of mixing a crosslinkable monomer with a polyimide precursor.
For example, there is a method of adding a quinonediazide compound to a polyamic acid, or polyamic acid ester or polyimide which has an acid group in a branched chain. However, although the polyamic acid is excellent in solubility for an alkali developer, it is problematic in reduction in a film upon development. Accordingly, amine, etc. has to be added to the polyamic acid. Further, the polyimide or the polyamic acid ester which has an acid group in a branched chain is excellent in resolution, etc., but problematic in that an absorption factor of a final hardening film is high or an alkali-proof property is deteriorated because the acid group remains in polymers even after the hardening.